The present invention relates to a new and improved electromagnetic apparatus and more particularly to an electromagnetic contactor having a core with a shading ring.
Electromagnetic contactors commonly have a laminated metal core with a shading ring. The shading ring provides magnetic flux which is out of phase with magnetic flux from the core. The use of the shading ring diminishes chattering or noise during operation of the contactor under the influence of an alternating current. Electromagnetic contactors having cores with shading rings are disclosed in U.S. Pat. Nos. 2,053,129; 3,283,275; 4,030,056; 4,525,694; and 4,760,364.
Copper shading rings have a relatively short operating life. This is due to fatigue fracture of the copper shading rings under the influence of mechanical vibration. However, copper shading rings have a high conductivity and, for that reason, the relatively short operating life of copper shading rings has been tolerated. In an effort to increase shading ring operating life, U.S. Pat. No. 2,053,129 suggests forming a shading ring of a copper-beryllium alloy.